A known vehicle seat belt system is a three-point continuous loop seat belt system. A three-point continuous loop seat belt system includes a seat belt retractor and a length of belt webbing. The belt webbing extends from the retractor through a D-ring fixed to the vehicle and then down to an anchor point near the vehicle floor. A belt latch is slidable along the length of belt webbing between the D-ring and the anchor point. To use the seat belt system, a vehicle occupant grasps the belt latch and inserts it into a buckle. When the belt latch is fastened in the buckle, a portion of the belt webbing extends across the lap of the vehicle occupant and a portion of the belt webbing extends diagonally across the torso of the vehicle occupant. When the belt latch is released from the buckle, the belt webbing is wound onto the retractor.
The belt latch should slide along the belt when the occupant moves the belt latch toward the buckle. The belt latch should also slide along the belt after the occupant unlocks the belt latch from the buckle so that the retractor can fully wind up the belt. The refractor would otherwise carry the belt latch upwardly to the D-ring, whereupon further movement of the belt would be prevented as the D-ring blocked further movement of the belt latch.
However, in the event of an accident it can be advantageous to separate the lap section of the belt webbing from the breast section, i.e. to block the belt webbing in the belt latch. Thus, at the event of a vehicle collision, when the belt webbing is subject to a predetermined load the belt latch should cinch the belt webbing, that is, block movement of the belt webbing through the belt latch. This cinching action helps to restrain movement of the vehicle occupant in the event of a vehicle collision in such a way that it may eliminate the need to use an expensive and complicated pyrotechnical seat-belt tensioner.
EP1983857 discloses such a belt latch for a safety belt that has a connecting plate for connecting the belt latch to a belt buckle, a basic latch body connected rigidly to the connecting plate, and further a deflecting and clamping element with a deflecting edge and a clamping edge. The deflecting and clamping element is arranged on the basic latch body in such a manner that it executes a rotational movement about an axis of rotation in relation to the basic latch body from a first deflecting position to a second clamping position when a defined belt force is exceeded. The deflecting and clamping element has a convex outer surface. In order to be able to achieve a low weight for the belt latch and, in particular, for the deflecting and clamping element, the deflecting and clamping element is mounted on the basic latch body by means of the convex outer surface. The basic latch body has the shape of a longitudinally cut-open hollow cylinder, i.e. the shape of a groove. It exhibits a concave inner surface with a cross-section in the shape of a partial circle. The bending and clamping element is positioned on the concave inner surface of the basic latch body, which serves as sliding surface. The bending and clamping element is also formed as a groove and the radius of its outer surface corresponds to the radius of the inner surface of the basic latch body. If a defined threshold force, which the belt webbing exercises on the bending edge is exceeded, breaking noses retaining the bending and clamping element break and the belt webbing presses the bending and clamping element into the clamping position. The greater the force within the belt webbing, the greater is also the clamping force, so that the aim of decoupling between lap and upper body section of the belt webbing is achieved.
As the basic latch body of EP1983857 has the shape of a longitudinally cut-open hollow cylinder with the bending and clamping element positioned on the inner surface thereof and the bending and clamping element also formed as a groove where the radius of its outer convex surface corresponds to the radius of the concave inner surface of the basic latch body there is a risk of dirt and dust entering the functional area of the basic latch body. The presence of contaminations within the functional area of the basic latch body could potentially cause a malfunction problem, where the bending and clamping element would be prevented from properly executing its clamping function in the case of an accident. The open nature thereof also increases the risk of other objects being jammed into the functional area of the basic latch body, which could potentially interfere with the clamping abilities of the bending and clamping element.